Hi, We are traveling from Zurich Airport to Grindelwald, then after 5 days to Zermatt, and finally after 4 days back to Zurich airport beginning December 16. Is it advisable to travel by rail using a Swiss Pass? Looking at the rail maps it appears to be possible and easy to make connections. Am I reading this right or is there a better way to travel? I really appreciate any help you can offer...

Yes, the trains are the best way to travel: safe, clean, eco-friendly and wonderful views. There is a long tunnel on your way from Grindelwald to Zermatt, but if you want to skip that and enjoy more views you can take the local train from Spiez to Brig via Kandersteg. There are no extra changes involved, it just takes longer.

A 3-day Swiss Saver Flexi Pass fits your needs: the 3 transfers are free, and you can get discounted tickets on the days in between for day trips. See the link for all details please.